docs: def available(self, **kwargs):
          """
          Find available dedicated numbers to buy. Returns dictionary like this:
          ::
              {
                  "numbers": [
                  "12146124143",
                  "12172100315",
                  "12172100317",
                  "12172100319",
                  "12172100321",
                  "12172100323",
                  "12172100325",
                  "12172100326",
                  "12172100327",
                  "12172100328"
                ],
                "price": 2.4
              }
  
          :Example:
  
          numbers = client.numbers.available(country="US")
  
          :param str country: Dedicated number country. Required.
          :param str prefix:  Desired number prefix. Should include country code (i.e. 447 for GB)
          """
          uri = "%s/%s" % (self.uri, "available")
          response, instance = self.request("GET", uri, params=kwargs)
          return instance